1. Field of the Invention
The present invention relates to supersonic combustion engines and, in particular, to a supersonic engine having means for providing a spatially controlled combustion initiation and distribution for a controlled relatively rapid combustion.
2. Prior Art
Air breathing propulsion at high flight Mach number, such as above Mach 5, can usefully employ a ramjet with internal supersonic combusting flow. The present invention specifically addresses this type of engine family. Supersonic jet engines generally include ramjets, pulsejets, and rocket motors. Various different types of supersonic jet engines exist in the prior art as well as different types of ignition methods in the reaction engine family. Combustion instability in supersonic combustion jet engines, in the form of pressure waves coupled with fuel/air chemical heat release, is a well known and often severe problem with supersonic combustor design and operation. U.S. Pat. No. 4,035,131 by Cerkanowicz discloses a method and apparatus for controlling the initiation and completion of self-sustaining combustion in fuel/oxidizer mixtures in a gas turbine engine through the use of ultraviolet radiation absorbed throughout the mixture. Cerkanowicz also discloses use of multiple ultraviolet sources used in sequence or phased according to preselected timing sequences. U.S. Pat. No. 2,587,331 by Jordan discloses disassociation and ionization of gaseous particles. U.S. Pat. No. 4,173,122 by Wilkinson discloses an intermittent burning ramjet engine where fuel is cyclically ignited at a predetermined frequency. U.S. Pat. No. 3,651,644 by Breen et al. discloses initiation of decomposition of monopropellant fuels or oxidizers through the use of an electric potential. U.S. Pat. No. 3,449,913 by Grebe discloses ignition of fuel by use of spark discharge along the length of the combustion chamber, laser beams, positive ion beams and electron gun beams. U.S. Pat. No. 3,621,658 by Grebe discloses encompassing the combustion zone with a magnetic field. U.S. Pat. No. 4,726,336 by Hoppie et al. discloses an arrangement and method for enabling hypergolic combustion of a fuel mixture in the combustion chamber of a combustion device such as an internal combustion engine by irradiation of the fuel and/or of the fuel-air mixture with a beam of ultraviolet radiation to produce disassociation of a relatively high proportion of the fuel molecules to enable hypergolic combustion. Various arrangements are disclosed for accomplishing UV irradiation of the fuel in the context of an internal combustion piston engine, and a mercury vapor lamp or a laser are alternatively employed as a UV beam generator.
Various problems exist with supersonic combustion jet engines. One problem is that structural flame holders or high local static temperature which are necessary for controlled ignition in supersonic combustors having high Mach number gas flow therethrough decrease efficiency and limit flight envelopes for flight vehicles propelled by supersonic jet engines.
Another problem is that supersonic jet propulsion for hypersonic flight requires distributed heat release along the flow path. Heat distribution must be varied with flight conditions, such as velocity, altitude and acceleration, for optimum performance. Prior art supersonic jet engines require variation of fuel distribution to produce selective localized initiation along the length of the flow duct to control heat release and thus require a multiplicity of fuel injectors and controls to approximate optimized performance.
Another problem is that Hydrogen is considered the optimum fuel for supersonic combustion because, in part, it ignites with the use of relatively low energy ignition and combusts more rapidly than other fuels. However, other fuels such as hydrocarbons; e.g.: liquid methane, although potentially advantageous in terms of vehicle design because of higher density and decreased fuel tank volume with resulting potential decreases in vehicle drag losses and fuel tank mass, cannot be as rapidly combusted as hydrogen in an acceptable gas flow time scale in a supersonic jet engine.
It is therefore an objective of the present invention to provide a supersonic jet engine and method for controlled spatially distributed ignition in supersonic combustor flows without dependence on structural flame holders or relatively high local static temperature.
It is another objective of the present invention to provide a supersonic jet engine and method for controlling spatial heat release distribution in supersonic combustion for optimum engine performance.
It is another objective of the present invention to provide a supersonic jet engine and method with ignition and combustion rate enhancement of fuels in supersonic combustion for allowing use of a variety of different fuels in supersonic jet engines.